This invention relates to a flashlight and more specifically to a flashlight with an automatic shut-off feature.
Flashlights are often mistakenly left ON which causes the batteries to run down, for example, when the flashlight is placed somewhere and forgotten while it is ON, or when a user enters a well lit room and neglects to turn the flashlight OFF.
To overcome the foregoing undesirable results, U.S. Pat. Nos. 3,535,282; 4,875,147; and 5,138,538 propose flashlights that automatically shut off. To implement the shut off feature, the referenced patents propose methods involving a shut-off delay means or means such as a button that keeps the flashlight ON only while it is being held down by the user. Such methods require the shut off feature to be repeatedly reset manually by the user, which is a drawback.
It would thus be desirable to have a flashlight with an automatic shut off feature that does not include the drawbacks of the prior art flashlights.
A flashlight according to the present invention includes a start button, a shut-off timer, and a motion sensor. When the start button is momentarily pressed and released, the flashlight is turned ON and the shut-off timer is set. If the timer is not reset during a predetermined time interval, the light will automatically turn off. The timer can be reset either by the user again pressing the start button, or by operation of the motion sensor due to movement of the flashlight after the predetermined interval of time has elapsed.
To detect the motion of the flashlight a photocell sensor is used to look at the reflected light from the flashlight beam. The small changes of reflected light are sensed to confirm that the flashlight is in use to reset the timer. However, if the flashlight is laid down the reflected light will become stable and the timer circuit will be allowed to timeout and shut off the light.
According to another aspect of the invention, a locking detent or the like can also be provided so that by positive action of the user, the timer can be overridden. This allows the light to remain ON even if it is set down, if the user desires.
According to a further aspect of the invention, the photocell receives light from the side of the flashlight and when the environment around the flashlight is sufficiently bright it will allow the timer to timeout unless the start button is held.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.